The invention relates to a flow meter device having a first flow meter, which works according to the Coriolis principles and is provided with a first measuring tube, and a second flow meter, which works according to the Coriolis principle and is provided with a second measuring tube.
A flow meter device of this type is known from W. Kiehl, “Difference measurement using Coriolis mass flowmeters,” Flow Meas. Instrum., Vol. 2, April 1991, pp. 135 to 138. The use of two Coriolis flow meters is advantageous, for example, whenever the difference between two mass flows is to be determined. Determining this difference is useful if one wants to get information about a leak, for example.
To measure the difference, the first flow meter is used to measure a first mass flow and a second flow meter to measure the second mass flow, and the difference between the two mass flows is then calculated.
To ensure that the conditions created for the two measurements are as similar as possible, the two separate flow meters are usually accommodated in the same housing. To simplify production, the designs of the two flow meters are practically identical. This also facilitates the subsequent analysis of the individual signals.
However, when two identical flow meters are used in the same housing, problems may arise by the two flow meters influencing each other. In flow meters that work according to the Coriolis principle vibrations are produced. These vibrations also act on the measuring tubes. The phase difference between the vibrations along different sections of the measuring tube is a measure of the mass flow. Under unfavorable circumstances, however, these vibrations are also transmitted through the common housing from one flow meter to the other. If both flow meters vibrate at the same frequency, this transmission causes significant interference and can distort the flow measurement results.